JP2012064366A - Flat-shaped nonaqueous secondary battery and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flat-shaped nonaqueous secondary battery with a high capacity and a manufacturing method thereof.SOLUTION: The flat-shaped nonaqueous secondary battery has an electrode group comprising a plurality of positive electrodes and a plurality of negative electrodes laminated alternately with separators interposed and a nonaqueous electrolyte solution, all in a space formed of an outer case and a sealing case both are in a circular shape in a plan view, and of an insulation gasket. The positive electrode and the negative electrode have a respective body part and a current collector tab part protruding from the body part in a plain view and narrower in width than the body part. The electrode group is not provided with a binding tape to bind the whole, with a 0.01-0.2 mm difference between the inner diameter of the insulation gasket and the maximum diameter of the body part of the negative electrode in the electrode group. The flat-shaped nonaqueous secondary battery can be manufactured by a method of the present invention having a process of forming an electrode group in a sealing case with an insulation gasket mounted.

Description

  The present invention relates to a high capacity flat non-aqueous secondary battery and a method for manufacturing the same.

  In a flat non-aqueous secondary battery generally referred to as a coin-type battery or a button-type battery, an electrode group in which a positive electrode and a negative electrode are opposed to each other with a separator interposed therebetween, and a non-aqueous electrolyte solution are provided in an outer case. And a structure accommodated in a space formed by a sealing case and an insulating gasket (Patent Document 1, etc.).

  In the flat non-aqueous secondary battery as described above, a positive electrode mixture layer or a negative electrode agent layer is formed on one or both surfaces of the current collector on the positive electrode and the negative electrode, and a part of the current collector is mixed with the positive electrode mixture. It is exposed without forming a layer or a negative electrode agent layer, and this is used as a current collecting tab. The current collecting tabs of each positive electrode and each negative electrode are welded together, and these collected current collecting tabs are connected to terminals. There are some which are electrically connected by welding or the like to the inner surface of the outer case or the sealing case that also serves as a material (for example, Patent Document 1).

JP 2003-142161 A

  A flat non-aqueous secondary battery having a stacked electrode group is manufactured through a process in which, for example, a positive electrode, a negative electrode, and a separator are sequentially stacked to form an electrode group once and accommodated in a battery case. In consideration of the ease of insertion of the electrode group into the battery case, the inner diameter of the battery case (inner diameter of the insulating gasket) and the outer diameter of the electrode group (especially the outside of the negative electrode constituting the electrode group) There is a certain degree of difference in diameter).

  By the way, in recent years, as the application range of flat non-aqueous secondary batteries has expanded, there has been a demand for, for example, downsizing. However, in such a small flat non-aqueous secondary battery, the outer diameter of the electrode group, that is, the electrode When the outer diameter is reduced, the influence on the capacity reduction due to this is large, and it is difficult to construct a high capacity battery.

  For this reason, there is a need for the development of technology that can increase the capacity even for small flat non-aqueous secondary batteries.

  This invention is made | formed in view of the said situation, The objective is to provide a high capacity flat nonaqueous secondary battery, and its manufacturing method.

  The flat non-aqueous secondary battery of the present invention that has achieved the above object is formed by caulking and sealing a circular outer case in plan view and a circular sealing case in plan view through an insulating gasket. In the space, a plurality of positive electrodes and a plurality of negative electrodes are alternately stacked via separators, and an electrode group in which the outer case and the sealing case are substantially parallel to each other and a flat surface having a non-aqueous electrolyte The positive electrode has a main body portion and a current collecting tab portion that protrudes from the main body portion in a plan view and is narrower than the main body portion. A positive electrode mixture layer containing a positive electrode active material is formed on one or both surfaces of the current collector, and the positive electrode current collector tab portion has a positive electrode mixture layer formed on the current collector. The negative electrode protrudes from the main body portion in a plan view. A negative electrode agent layer containing a negative electrode active material on one side or both sides of the current collector, and the negative electrode body layer has a current collecting tab portion that is narrower than the main body portion. In the current collecting tab portion, a negative electrode layer is not formed on the current collector, and the electrode group does not have a binding tape that stops the whole, the inner diameter of the insulating gasket, and the electrode group The difference with the largest diameter in the main-body part of the negative electrode to have is 0.01-0.2 mm.

  The manufacturing method of the present invention is a method of manufacturing the flat non-aqueous secondary battery of the present invention, in which a negative electrode and a positive electrode are placed in a sealing case equipped with an insulating gasket, and a separator is provided between the negative electrode and the positive electrode. In this case, the electrode assembly is formed by sequentially inserting and laminating the electrode group.

  In the battery industry, a flat battery with a diameter larger than the height is called a coin-type battery or a button-type battery, but there is a clear gap between the coin-type battery and the button-type battery. There is no difference, and the flat non-aqueous secondary battery of the present invention includes both coin-type batteries and button-type batteries.

  ADVANTAGE OF THE INVENTION According to this invention, a high capacity | capacitance flat type non-aqueous secondary battery and its manufacturing method can be provided.

It is a longitudinal cross-sectional view which represents typically an example of the flat non-aqueous secondary battery of this invention. It is a principal part cross-sectional enlarged view of FIG. It is a top view which represents typically an example of the positive electrode which concerns on the flat nonaqueous secondary battery of this invention. It is a top view which represents typically an example of the negative electrode which concerns on the flat nonaqueous secondary battery of this invention. It is a top view which represents typically an example of the separator which concerns on the flat nonaqueous secondary battery of this invention. It is a longitudinal cross-sectional view which represents typically the other example of the flat nonaqueous secondary battery of this invention.

  1 and 2 schematically show an example of the flat non-aqueous secondary battery of the present invention. FIG. 1 is a longitudinal sectional view showing a cross section of a battery case (outer case 2 and sealing case 3) and an insulating gasket 4 part of a flat non-aqueous secondary battery. FIG. 2 is an enlarged view of the main part of FIG. Furthermore, the electrode group is shown in cross section. As shown in FIGS. 1 and 2, the flat non-aqueous secondary battery 1 is formed by laminating the positive electrode 5 and the negative electrode 6 so that their planes are substantially parallel (including parallel) to the flat plane of the battery, A laminated electrode group in which the outermost two electrodes are negative electrodes 6 (negative electrode 6B) and a nonaqueous electrolyte (not shown) are an outer case 2 that also serves as a positive electrode terminal, a sealing case 3 that also serves as a negative electrode terminal, and insulation. It is accommodated in a space (sealed space) formed by the gasket 4. The sealing case 3 is fitted to the opening of the outer case 2 via an insulating gasket 4, and the opening end of the outer case 2 is tightened inward, whereby the insulating gasket 4 contacts the sealing case 3. Thereby, the opening part of the exterior case 2 is sealed, and the inside of the battery has a sealed structure. The outer case 2 and the sealing case 3 are made of a metal such as stainless steel, and the insulating gasket 4 is made of an insulating resin such as polypropylene.

  1 and 2, the outer case 2 also serves as a positive electrode terminal, and the sealing case 3 also serves as a negative electrode terminal. However, in the battery of the present invention, for example, depending on the configuration of the electrode group, the outer case 2 May also serve as the negative electrode terminal, and the sealing case may also serve as the positive electrode terminal.

  FIG. 3 schematically shows a plan view of the positive electrode 5. The positive electrode 5 has a main body 5a and a width larger than that of the main body 5a projecting from the main body 5a in plan view (in the vertical direction in FIG. 3). And a current collecting tab portion 5b having a narrow length.

  In the main body 5a of the positive electrode 5, a positive electrode mixture layer 51 containing a positive electrode active material or the like is formed on both surfaces of a current collector (52 in FIG. 2). In the current collecting tab portion 5b of the positive electrode 5, the positive electrode mixture layer is not formed on the surface of the current collector 52, and the current collector 52 is exposed. In the batteries shown in FIGS. 1 and 2, since the outermost electrode in the electrode group is a negative electrode, the positive electrode mixture is formed on both surfaces of the current collector 52 in the main body 5a of all the positive electrodes 5. Although the layer 51 is formed, for example, one of the outermost electrodes in the electrode group (more specifically, the electrode on the exterior case side or the sealing case side that also serves as the positive electrode terminal) may be used as the positive electrode. In this case, the outermost positive electrode in the electrode group may have a positive electrode mixture layer only on one surface (surface inside the battery) of the current collector in the main body. In this case, the exposure of the positive electrode current collector on the outermost side of the electrode group and the inner surface of the outer case or sealing case that also serves as the positive electrode terminal can be directly connected or welded to each other.

  In addition, although the separator 7 is arrange | positioned on both surfaces of the positive electrode 5 which the both sides are facing the negative electrode 6, only the positive electrode arrange | positioned in the outermost side of an electrode group, ie, one side (one side), has opposed the negative electrode. With respect to the positive electrode, separators may be disposed on both surfaces thereof (further, a joint portion described later may be formed on these two separators), or the separator may be disposed only on the surface facing the negative electrode. Absent.

  4 schematically shows a plan view of the negative electrode 6. The negative electrode 6 has a width that is larger than the main body 6a and the main body 6a protruding from the main body 6a in plan view (upper and lower in FIG. 4). Current collecting tab portion 6b having a narrow direction length).

  As for the main-body part 6a of the negative electrode 6, the negative electrode agent layer 61 containing a negative electrode active material etc. is formed in the single side | surface or both surfaces of a collector (62 in FIG. 2). And the current collection tab part 6b of the negative electrode 6 does not have the negative electrode agent layer formed in the surface of the electrical power collector 62, and the electrical power collector 62 is exposed.

  In the battery shown in FIG. 1 and FIG. 2, the upper and lower ends of the electrode group are negative electrodes 6B and 6B, and these negative electrodes 6B and 6B are provided on only one side of the current collector 62 (the inner surface of the battery). A layer 61 is provided. On the other hand, the negative electrode 6 </ b> A arranged on the electrode group other than the upper and lower ends has negative electrode agent layers 61 and 61 on both surfaces of the current collector 62.

  Further, in the battery shown in FIG. 1 and FIG. 2, the current collecting tab portions 6b of all the negative electrodes 6 are collected and on the negative electrode 6B located on the outermost side on the exterior case 2 side in the electrode group (FIGS. 1 and 2). The outer negative electrode 6B is folded back to the outer case 2 side. An insulating material (insulating seal) 8 made of a tape formed of polyethylene terephthalate (PET), polyimide, or the like is disposed on the outer case 2 side of the current collecting tab portion 6b of each negative electrode 6 that is folded back. . Further, the exposed surface of the current collector 62 on the sealing case side (in FIGS. 1 and 2) of the negative electrode 6 </ b> B (the upper negative electrode 6 </ b> B in FIGS. 1 and 2) located on the outermost side on the sealing case 3 side in the electrode group. , The upper surface) and the inner surface of the sealing case 3 are electrically connected by direct contact or the like.

  Further, in the battery shown in FIGS. 1 and 2, the current collecting tab portions 5b of all the positive electrodes 5 are collected and on the insulating material 8 arranged on the exterior case 2 side in the electrode group (in FIGS. 1 and 2, It is folded back to the lower side of the insulating material 8 arranged below the lower negative electrode 6B. The folded current collecting tab portion 5b of each positive electrode 5 and the inner surface of the outer case 2 are electrically connected, for example, by direct contact.

  As described above, particularly in a small flat non-aqueous secondary battery, from the viewpoint of increasing capacity, for example, it is desired to increase the occupied volume of the positive and negative electrodes by reducing the gap between the insulating gasket and the electrode group as much as possible. . However, if the gap between the insulating gasket and the electrode group is reduced, when the electrode group is formed and then housed in the battery case, the electrode group can be satisfactorily inserted into the sealing case fitted with the insulating gasket, or the electrode group It becomes impossible to satisfactorily cover the sealing case fitted with the insulating gasket on the outer case that accommodates. In addition, the stacked electrode group of the flat non-aqueous secondary battery includes at least the upper and lower surfaces of the electrode group for the purpose of preventing the position of each electrode from shifting when accommodated in the battery case. It is common practice to attach a binding tape to the top and stop the whole. However, if the gap between the insulating gasket and the electrode group is reduced, the end of the binding tape aligns the outer case with the sealing case covered with the insulating gasket. There is a possibility that it will not be able to be caulked well.

  On the other hand, the flat non-aqueous secondary battery of the present invention can be manufactured, for example, by the method of the present invention (detailed later) having a step of forming an electrode group in a sealing case equipped with an insulating gasket. In addition, the electrode group formed separately can be manufactured without the process of housing in the battery case. Therefore, in the electrode group, it is possible to avoid the use of a binding tape that is used as a whole. The difference from the diameter can be 0.2 mm or less, and the gap between the insulating gasket and the electrode group can be reduced to reduce the size of the flat non-aqueous secondary battery of various sizes including a small one. The productivity can be increased while increasing the capacity.

  However, if the gap between the insulating gasket and the electrode group is too small, the productivity of the battery is adversely affected. Therefore, in the flat non-aqueous secondary battery of the present invention, the inner diameter of the insulating gasket and the maximum of the main body in the negative electrode The difference from the diameter is set to 0.01 mm or more.

  The “maximum diameter of the main body portion in the negative electrode” in the present specification means the diameter of a portion of the substantially circular main body portion where the outer peripheral edges facing each other across the center are arc portions.

  That is, in the battery of the present invention, the planar shape of the negative electrode main body is preferably substantially circular, and the planar shape of the positive electrode main body is preferably substantially circular. In addition, in the main body part of the negative electrode and the positive electrode, the part corresponding to the place where the current collecting tab part of the counter electrode is arranged is shown in FIGS. 3 and 4 in order to prevent contact with the current collecting tab part of the counter electrode. It is preferable that the shape is cut off.

  In the flat nonaqueous secondary battery of the present invention, both the outer case and the sealing case are circular in plan view. As described above, the flat non-aqueous secondary battery of the present invention is preferably manufactured by the method of the present invention in which the electrode group is formed in the sealing case equipped with the insulating gasket, and the binding tape for stopping the entire electrode group Do not use. Therefore, in the battery of the present invention, in addition to reducing the difference between the maximum diameter of the main body portion of the insulating gasket and the negative electrode as described above, the outer case and the sealing case are circular, and the positive and negative current collecting tabs Even if a space is generated at the location where the part is present, it is possible to suppress the displacement of the positive and negative electrodes constituting the electrode group.

  In the flat non-aqueous secondary battery of the present invention, as shown in FIGS. 1 and 2, the outer case serves also as the positive electrode terminal, and the sealing case serves also as the negative electrode terminal, and the outermost side of the electrode group. The two electrodes located on the outermost side of the electrode group are formed with the negative electrode agent layer only on the surface opposite to the outermost side of the electrode group in the main body portion. The negative electrode layer is not formed on the current collector on the outermost surface of the electrode group and the current collecting tab in the main body, and the negative electrode other than the negative electrode on the outermost side of the electrode group Has a negative electrode agent layer formed on both surfaces of the main body, and the current collector tab portion has no negative electrode agent layer formed on the current collector. The tab part is gathered and folded back on the negative electrode located on the outermost side of the outer case side of the electrode group. An insulating material is disposed on the exterior case side of each current collecting tab portion of the negative electrode, and the exposed surface of the current collector in the sealing case side of the negative electrode located on the outermost side of the sealing case side of the electrode group, The inner surface of the sealing case is electrically connected, and the current collecting tab portions of the positive electrode are collected and folded on the insulating material disposed on the outer case side of the electrode group to be electrically connected to the outer case. It is preferable. In the case of such an embodiment, the production by the method of the present invention described later becomes easy.

  In the electrode group according to the battery of the present invention, the collected current collecting tabs of the positive electrodes or the collected current tab portions of the collected negative electrodes may be joined to each other by welding or the like.

  Further, in the electrode group according to the battery of the present invention, in the case of the above aspect in which both of the two outermost electrodes are negative electrodes (in the case of the aspect shown in FIGS. 1 and 2), each of the collected positive electrodes The electric tab portion may be joined to each other by welding or the like before the folded portion (end side), and the joined current collecting tab portion may be bonded with an insulating material and an adhesive.

  In the battery of the present invention, as in the case of a normal battery, the separator may have a single-layer or multilayer porous film interposed between the positive electrode and the negative electrode, for example. As shown, it is preferable that the two separators 7 and 7 arranged on both surfaces of the positive electrode 5 (the positive electrode 5 opposite to the negative electrode 6 on both sides) have a joint at their peripheral portions. That is, it is preferable that the positive electrode whose both sides are opposed to the negative electrode is accommodated in a bag-shaped separator. In this case, since the lamination process of the positive electrode, the negative electrode, and the separator for forming the electrode group can be reduced, the production of the battery of the present invention is facilitated particularly by the method of the present invention described later.

  In FIG. 5, the top view of the separator which formed the junction part in a part of peripheral part is shown typically. In FIG. 5, assuming the case of a stacked electrode group in which the positive electrode, the negative electrode, and the separator are stacked together with the separator 7, the positive electrode 5 disposed under the separator 7 is indicated by a dotted line, The current collection tab part 6b which concerns on the negative electrode arrange | positioned below is shown with the dashed-dotted line. Further, the positive electrode 5 shown in FIG. 5 has both sides (both sides) opposed to the negative electrode in the electrode group. Although not shown in FIG. 5, when the electrode group is used, the upper side of the separator 7 (in the drawing) In the forward direction), at least a negative electrode is arranged.

  As shown in FIG. 5, the separator 7 and other separators disposed on the lower side (in the depth direction in the figure) via the positive electrode 5 (indicated by a dotted line in the figure) were welded to each other at the peripheral edge thereof. It has a joint 7c (indicated by a lattice pattern in the figure). That is, the separator 7 and the separator disposed below the separator 7 are welded to each other at the peripheral edge to form a bag shape, and the positive electrode 5 is accommodated therein.

  The separator 7 protrudes from the main body part 7a (that is, the main body part 7a having a larger area in plan view than the main body part 5a of the positive electrode 5) covering the entire surface of the main body part 5a of the positive electrode 5 and the main body part 7a. The electric tab portion 5b has an overhang portion 7b that covers at least a portion including a boundary portion with the main body portion 5a. Then, two separators (the separator 7 and the separator disposed below the positive electrode 5) disposed on both surfaces of the positive electrode 5 were welded to at least a part of the peripheral portion of the main body portion 7 a of the separator 7. A joint 7c is provided.

  The joining part for joining the two separators arranged on both sides of the positive electrode may be provided at the peripheral part of the separator main part, but the peripheral part of the separator overhanging part (the peripheral part of the separator overhanging part). Of these, a joint portion may also be provided on a portion along the protruding direction from the main body portion.

  The joining portion 7c may be formed by directly welding the peripheral portions of the two separators, but a layer made of a thermoplastic resin is interposed between the two separators, and 2 You may form by welding the separator of a sheet. However, in the latter case, depending on the type of thermoplastic resin that constitutes the layer interposed between the separators and the type of thermoplastic resin that constitutes the separator, the strength of the joint may be reduced. It is preferable to use the layer made of the same kind of resin as the thermoplastic resin constituting the separator. That is, when the separators are welded directly, or when the separators are welded via a layer composed of the same type of resin as the thermoplastic resin that constitutes the separator, the strength of the joint is determined by the strength of the separator itself. Since they are almost the same, for example, peeling at the joint that may occur due to vibration or the like when the battery is used can be satisfactorily suppressed, and a battery with higher reliability can be obtained.

  In addition, although all the peripheral parts which concern on the main part of a separator may be a junction part, as shown in FIG. 5, for example, as shown in FIG. You may leave as 7d and 7d. After the two separators are welded to form a bag, the positive electrode is accommodated therein, the positive electrode is disposed on one separator, and the separator is further disposed on the positive electrode. When the positive electrode is housed in a separator that is welded to form a bag, air may remain in the separator. However, when manufacturing a battery using such a positive electrode, when the positive electrode case and the negative electrode case are caulked, the residual air is well discharged out of the separator through the non-welded portions 7d and 7d. Occurrence of problems due to residual air in the separator (problems such as non-uniform reaction during power generation and reduced capacity) can be prevented.

  When providing a non-welding part in the peripheral part of a separator, it is preferable that the number shall be about 1-5 from a viewpoint of suppressing the productivity fall of a battery. Moreover, when providing a non-welding part in the peripheral part of a separator, the length of the outer edge of the non-welding part related to the main part of the separator is the total length of the outer edge related to the main part of the separator (the total length of the outer edge excluding the overhanging part). Is preferably about 15 to 60%. That is, in the main part of the separator, it is preferable that 40% or more (preferably 70% or more) of the entire length of the outer edge is a joined part, thereby ensuring good joining strength between the separators. Can do.

  In order to form a joint part at the peripheral part of two separators and to accommodate a positive electrode between these separators, when two separators are directly welded together to form a joint part, for example, one sheet It is possible to employ a method in which the positive electrode is overlaid on the separator, the separator is further overlaid thereon, and then the peripheral portions of these separators are welded. It is also possible to adopt a method in which two separators are stacked, the peripheral portions thereof are welded to join the separators, and then the positive electrode is inserted between these separators.

  On the other hand, when a layer composed of the same kind of resin as the constituent resin of the separator is interposed between the two separators and these are welded to form a joint, for example, the joint on one separator It is possible to adopt a method in which a film to be the layer is placed at a place where the layer is expected to be placed, a positive electrode is disposed on the separator, and a separator is further stacked thereon, and then the peripheral portions of these separators are welded. . In addition, a film to be the layer is placed in a place where it is planned to become a joint portion on one separator, and the separator and the film are previously welded. Adopting a method of laminating the peripheral portion by overlapping, or a method of inserting a positive electrode between these separators after forming a joined portion by interposing a film serving as the layer between two separators. You can also.

  For example, the peripheral edge of the separator can be welded by a hot press. In this case, the heating temperature may be a temperature higher than the melting point of the thermoplastic resin constituting the separator, but for example, the heating temperature is preferably 10 to 50 ° C. higher than the melting point. Moreover, about the time of a hot press, if a junction part can be formed satisfactorily, there will be no restriction | limiting, However, Usually, it shall be about 1 to 10 second.

  When a joint is formed at the peripheral edge of two separators disposed on both sides of the positive electrode (in the case of a bag-shaped separator), a main body of the negative electrode, and a main body of the separator disposed on both sides of the positive electrode However, it is preferable that they have substantially the same shape (including the same shape) in plan view. As a result, the difference between the inner diameter of the insulating gasket and the maximum diameter of the main portion of the bag-shaped separator containing the positive electrode is equivalent to the difference between the inner diameter of the insulating gasket and the maximum diameter of the main body portion of the negative electrode. The position of the bag-shaped separator containing the positive electrode is hardly displaced, and the reliability of the battery is further improved. Here, “substantially the same shape” means that there is a slight difference between the shape of the “negative electrode body” and the “main part of the separator”. Specifically, the positive electrode excluding the overhanging portion. The difference between the end of the separator that wraps the electrode and the dimension in the width direction at the end of the negative electrode excluding the current collecting tab is less than 5%.

The size of the battery of the present invention is not particularly limited, but the effect of the present invention is particularly remarkable when the opening area of the insulating gasket is very small, for example, 100 mm ² or less. However, since the battery having a very small opening area of the insulating gasket itself tends to be difficult to produce, the opening area of the insulating gasket according to the battery of the present invention is preferably 20 mm ² or more, for example.

  The positive electrode mixture layer of the positive electrode according to the battery of the present invention is a layer containing a positive electrode active material, a conductive additive, a binder and the like.

Examples of the positive electrode active material according to the battery of the present invention include Li _x CoO ₂ , Li _x NiO ₂ , Li _x MnO ₂ , Li _x Co _y Ni _1-y O ₂ , and Li _x Co _y M _1-y O _2. lithium transition metal composite such as _{Li x Ni 1-y M y} O 2, Li x Mn y Ni z Co 1-y-z O 2, Li x Mn 2 O 4, Li x Mn 2-y M y O 4 (However, in each of the above lithium transition metal composite oxides, M is at least one selected from the group consisting of Mg, Mn, Fe, Co, Ni, Cu, Zn, Al, and Cr.) It is a metal element, and 0 ≦ x ≦ 1.1, 0 <y <1.0, and 2.0 ≦ z ≦ 2.2.) These positive electrode active materials may be used individually by 1 type, and may use 2 or more types together.

  Moreover, as a conductive support agent of a positive electrode, carbon black, scale-like graphite, ketjen black, acetylene black, fibrous carbon etc. are mentioned, for example. Furthermore, examples of the binder for the positive electrode include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), carboxymethyl cellulose, and styrene butadiene rubber.

  For the positive electrode, for example, a positive electrode mixture obtained by mixing a positive electrode active material, a conductive additive, and a binder is dispersed in water or an organic solvent to prepare a positive electrode mixture-containing paste (in this case, the binder is preliminarily mixed with water or It may be dissolved or dispersed in a solvent and mixed with a positive electrode active material or the like to prepare a positive electrode mixture-containing paste), and the positive electrode mixture-containing paste is made of metal foil, expanded metal, plain weave metal mesh, etc. It is manufactured by forming a positive electrode mixture layer by applying it to one or both sides of a current collector, drying it, and then press-molding it. However, the method for manufacturing the positive electrode is not limited to the above-described method, and other methods may be used.

  As a composition of the positive electrode, for example, in 100% by mass of the positive electrode mixture constituting the positive electrode, the positive electrode active material is 75 to 90% by mass, the conductive additive is 5 to 20% by mass, and the binder is 3 to 15% by mass. Is preferred. Moreover, it is preferable that the thickness of a positive mix layer is 30-200 micrometers, for example.

  The material for the current collector of the positive electrode is preferably aluminum or an aluminum alloy. From the viewpoint of reducing the total thickness of the positive electrode and increasing the number of layers of the positive electrode and the negative electrode in the battery to increase the facing area between the positive electrode mixture layer and the negative electrode agent layer and improving the load characteristics of the battery, It is preferable to use a metal foil for the current collector. Moreover, it is preferable that the thickness of a collector is 8-20 micrometers, for example.

  Examples of the negative electrode according to the battery of the present invention include a negative electrode having lithium, a lithium alloy, a carbon material capable of occluding and releasing lithium ions, lithium titanate, and the like as an active material.

  Examples of the lithium alloy that can be used for the negative electrode active material include lithium alloys that reversibly alloy with lithium, such as lithium-aluminum and lithium-gallium, and the lithium content is, for example, 1 to 15 atomic%. Is preferred. Examples of the carbon material that can be used for the negative electrode active material include artificial graphite, natural graphite, low crystalline carbon, coke, and anthracite.

The lithium titanate that can be used for the negative electrode active material is represented by the general formula Li _x Ti _y O ₄ , and x and y are 0.8 ≦ x ≦ 1.4 and 1.6 ≦ y ≦ 2.2, respectively. Lithium titanate having a stoichiometric number is preferable, and lithium titanate having a stoichiometric number of x = 1.33 and y = 1.67 is particularly preferable. The lithium titanate represented by the general formula Li _x Ti _y O ₄ can be obtained, for example, by heat-treating titanium oxide and a lithium compound at 760 to 1100 ° C. As the titanium oxide, either anatase type or rutile type can be used, and examples of the lithium compound include lithium hydroxide, lithium carbonate, and lithium oxide.

  When the negative electrode active material is lithium or a lithium alloy, the negative electrode is formed by bonding the lithium or lithium alloy to a current collector such as a metal network to form a negative electrode layer made of lithium or lithium alloy on the surface of the current collector. Can be obtained. On the other hand, when a carbon material or lithium titanate is used as the negative electrode active material, for example, a negative electrode composite obtained by mixing a carbon material or lithium titanate with a binder as the negative electrode active material and, if necessary, a conductive additive. The negative electrode mixture-containing paste is prepared by dispersing the agent in water or an organic solvent (in this case, the binder is previously dissolved or dispersed in water or solvent, and mixed with the negative electrode active material or the like to contain the negative electrode mixture) The paste containing the negative electrode mixture may be applied to a current collector made of metal foil, expanded metal, plain weave metal mesh, etc., dried, and then pressed to form a negative electrode layer (negative electrode composite). The negative electrode can be produced by forming an agent layer. However, the manufacturing method of the negative electrode is not limited to the above-described method, and other methods may be used.

  In addition, as a binder and conductive support agent which concern on a negative electrode, the various binders and conductive support agent which were illustrated previously as what can be used for a positive electrode can be used.

  The composition of the negative electrode when a carbon material is used as the negative electrode active material is, for example, that the carbon material is 80 to 95% by mass and the binder is 3 to 15% by mass in 100% by mass of the negative electrode mixture constituting the negative electrode. Moreover, when using together a conductive support agent, it is preferable that a conductive support agent shall be 5-20 mass%. On the other hand, the composition of the negative electrode when lithium titanate is used as the negative electrode active material is, for example, 75 to 90% by mass of lithium titanate and 3 to 15% by mass of the binder in 100% by mass of the negative electrode mixture constituting the negative electrode. In addition, when a conductive auxiliary is used in combination, the conductive auxiliary is preferably 5 to 20% by mass.

  The thickness of the negative electrode layer (including the negative electrode mixture layer) in the negative electrode is preferably 40 to 200 μm, for example.

  The material for the current collector of the negative electrode is preferably copper or a copper alloy. From the viewpoint of reducing the total thickness of the negative electrode and increasing the number of layers of the positive electrode and negative electrode in the battery to increase the facing area between the positive electrode mixture layer and the negative electrode agent layer, and improving the load characteristics of the battery, It is preferable to use a metal foil for the current collector. Moreover, it is preferable that the thickness of a collector is 5-30 micrometers, for example.

  A separator made of a microporous film made of a thermoplastic resin is used. As the thermoplastic resin constituting the separator, for example, polyolefins such as polyethylene (PE), polypropylene (PP), ethylene-propylene copolymer, polymethylpentene, and the like are preferable. From the viewpoint of arranging and welding the same type of resin as the constituent resin, the melting point, that is, the melting temperature measured using a differential scanning calorimeter (DSC) in accordance with the provisions of JIS K 7121 is 100. A polyolefin of ˜180 ° C. is more preferable.

  The form of the microporous film made of the thermoplastic resin constituting the separator may be any form as long as it has an ionic conductivity sufficient to obtain the required battery characteristics, but is a conventionally known solvent. An ion-permeable microporous film (a microporous film that is widely used as a battery separator) having a large number of pores formed by an extraction method, a dry method or a wet stretching method is preferable.

  The thickness of the separator is preferably, for example, 5 to 25 μm, and the porosity is preferably, for example, 30 to 70%.

  Examples of non-aqueous electrolytes for batteries include cyclic carbonates such as ethylene carbonate (EC), propylene carbonate, butylene carbonate, and vinylene carbonate; chain carbonate esters such as dimethyl carbonate, diethyl carbonate (DEC), and methyl ethyl carbonate. 1,2-dimethoxyethane, diglyme (diethylene glycol methyl ether), triglyme (triethylene glycol dimethyl ether), tetraglyme (tetraethylene glycol dimethyl ether), 1,2-dimethoxyethane, 1,2-diethoxymethane, tetrahydrofuran, etc. It is possible to use an electrolytic solution prepared by dissolving an electrolyte (lithium salt) in a concentration of about 0.3 to 2.0 mol / L in an organic solvent such as ether; That. The above organic solvents may be used alone or in combination of two or more.

Examples of the electrolyte include LiBF ₄ , LiPF ₆ , LiAsF ₆ , LiSbF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) Lithium salts such as ₂ are mentioned.

  The positive electrode, the negative electrode, and the separator are stacked and used as a stacked electrode group as shown in FIG. 1 and FIG. 2, and the current collecting tab portion of each positive electrode is the same in a plan view of the electrode group. It is preferable that the current collecting tabs of the negative electrodes are arranged so as to face in the same direction in the plan view of the electrode group. Thereby, current collection of the positive electrode and the negative electrode becomes easier.

  Furthermore, the current collecting tab portion of each positive electrode and the current collecting tab portion of each negative electrode only need to be arranged so as not to contact each other in a plan view of the electrode group, but these contacts are better suppressed, And from the viewpoint of making the production of the battery better, as shown in FIG. 5, the current collecting tab portion 5b of each positive electrode and the current collecting tab portion 6b of each negative electrode face each other in a plan view of the electrode group. More preferably, it is arranged at a position where

  There are a plurality of positive electrodes and negative electrodes in the electrode group, and the total number of layers of the electrode is at least 4, but it is also possible to make it more (5 layers, 6 layers, 7 layers, 8 layers, etc.) It is. However, if the number of stacked positive and negative electrodes is increased too much, the merit as a flat battery may be reduced. Therefore, it is usually preferable to have 40 layers or less.

  Further, in the flat non-aqueous secondary battery of the present invention, as shown in FIGS. 1 and 2, a portion of the insulating gasket facing the battery in the thickness direction of the battery inner surface and the sealing case (upper and lower in the figure). It is preferable that the battery inner surface of the portion facing the direction is on the same surface. The inner surface of the insulating gasket and the inner surface of the sealing case that faces the thickness direction of the battery serve as a guide when forming the electrode group. When it is on the surface, it is difficult for the negative electrode and the positive electrode accommodated in the bag-shaped separator to be displaced during the formation of the electrode group, and the productivity of the battery is improved.

  FIG. 6 is a longitudinal sectional view schematically showing another example of the flat non-aqueous secondary battery of the present invention. As shown in FIG. It is also preferable that the upper end of the surface in FIG. 6 reaches the vicinity of the inner surface of the sealing case 3. Specifically, the height of the inner surface of the insulating gasket 4 (the length in the vertical direction in FIG. 6). The shortest distance from the inner surface of the outer case 2 to the inner surface of the sealing case 3 (that is, the height of the space portion inside the battery case) is preferably 90% or more (100% or less). In such a case, since the inner surface of the battery of the insulating gasket 4 functions as a guide for suppressing displacement between the negative electrode and the bag-shaped separator containing the positive electrode when the electrode group is formed. Productivity is improved.

  The flat non-aqueous secondary battery of the present invention can be manufactured by the following manufacturing method of the present invention.

  The manufacturing method of the present invention includes a step of forming a group of electrodes by sequentially inserting and laminating a negative electrode and a positive electrode in a sealing case equipped with an insulating gasket, with a separator interposed between the negative electrode and the positive electrode. Have. In addition, when the junction part is formed in the peripheral part of two separators arrange | positioned on both surfaces of a positive electrode, ie, when a positive electrode is accommodated in a bag-shaped separator, a negative electrode and a bag-shaped separator The electrode group may be formed by sequentially inserting and laminating the positive electrode housed in the container into a sealing case fitted with an insulating gasket.

  After the electrode group is formed in the sealing case fitted with the insulating gasket by the above-mentioned process, for example, a nonaqueous electrolyte is put into the sealing case and the exterior of the opening of the sealing case (the opening of the insulating gasket) A flat non-aqueous secondary battery can be obtained by covering the case.

  The flat non-aqueous secondary battery of the present invention can be applied to the same use as a conventionally known flat non-aqueous secondary battery.

  Hereinafter, the present invention will be described in detail based on examples. However, the following examples do not limit the present invention.

Example 1
<Preparation of positive electrode>
A positive electrode was prepared using LiCoO ₂ as a positive electrode active material, carbon black as a conductive additive, and PVDF as a binder. First, LiCoO ₂ : 93 parts by mass and carbon black: 3 parts by mass were mixed, and the resulting mixture and PVDF: 4 parts were previously dissolved in N-methyl-2-pyrrolidone (NMP) and a binder solution Were mixed to prepare a positive electrode mixture-containing paste. The obtained positive electrode mixture-containing paste was applied to both surfaces of a positive electrode current collector made of an aluminum foil having a thickness of 15 μm by an applicator. When applying the positive electrode mixture-containing paste, the application part and the non-application part were continuously arranged every 5 cm, and the part that was the application part on the front surface was also the application part on the back surface. Subsequently, the applied positive electrode mixture-containing paste was dried to form a positive electrode mixture layer, and then roll-pressed and cut into a predetermined size to obtain a belt-like positive electrode. The positive electrode had a width of 40 mm, and the positive electrode mixture layer forming portion had a thickness of 140 μm.

  The shape of the belt-like positive electrode shown in FIG. 3 is such that the positive electrode mixture layer forming portion is a main body portion (arc portion diameter 6.2 mm) and the positive electrode mixture layer non-forming portion is a current collecting tab portion. The battery positive electrode was obtained.

<Accommodating battery positive electrode in bag-shaped separator>
A PE microporous membrane separator (thickness 16 μm) having the shape shown in FIG. 5 is arranged on both surfaces of the battery positive electrode, and the portion shown in FIG. 5 is welded by a hot press (temperature 170 ° C., press time 2 seconds). A joining part was formed in a part of the peripheral part of the main part concerning two separators, and the battery positive electrode was accommodated in the bag-like separator. In addition, the width | variety of the junction part which concerns on two separators was 0.25 mm. Further, 80% of the outer edge of the main part of the two separators was used as the joint. The diameter (maximum diameter) of the arc portion of the main portion of the bag-shaped separator containing the battery positive electrode was 7.20 mm.

<Production of negative electrode>
A negative electrode was prepared using graphite as the negative electrode active material and PVDF as the binder. A paste containing 94 parts by mass of graphite and a binder solution in which 6 parts by mass of PVDF were previously dissolved in NMP was mixed to prepare a negative electrode mixture-containing paste. The obtained negative electrode mixture-containing paste was applied to one or both sides of a negative electrode current collector made of a copper foil having a thickness of 10 μm by an applicator. In addition, when applying the negative electrode mixture-containing paste, when the coated part and the non-coated part are continuously applied every 5 cm and are applied to both sides of the current collector, the place where the coated part is the surface is the back side However, it was made to become an application part. Subsequently, the applied negative electrode mixture-containing paste was dried to form a negative electrode mixture layer, and then roll-pressed and cut into a predetermined size to obtain a strip-shaped negative electrode. The negative electrode had a width of 40 mm, and the negative electrode mixture layer forming portion had a thickness of 190 μm when formed on both sides of the current collector and 100 μm when formed on one side of the current collector.

  The belt-like negative electrode is formed so that the negative electrode mixture layer forming portion is a main body portion [arc portion diameter (maximum diameter) 7.20 mm], and the negative electrode mixture layer non-forming portion is a current collecting tab portion. The negative electrode for a battery having a negative electrode mixture layer on one side of the current collector and the negative electrode for a battery having a negative electrode mixture layer on both sides of the current collector were obtained.

<Battery assembly>
13 battery positive electrodes housed in the bag-shaped separator, 12 battery negative electrodes having a negative electrode mixture layer formed on both sides of the current collector, and battery electrode having a negative electrode mixture layer formed on one side of the current collector Prepare two negative electrodes (one of which is a PET film attached to the exposed surface of the current collector), and the negative electrode for the battery with the negative electrode mixture layer formed on one side of the current collector is the outermost The battery positive electrode and the battery negative electrode were alternately stacked in a sealing case equipped with an insulating gasket so as to be an electrode. Then, the current collecting tabs of the negative electrodes for each battery are welded together and then folded on the negative electrode on the opening side of the sealing case, and an insulating material (PET film having a thickness of 0.1 mm) is placed thereon, and each battery After the current collecting tabs of the positive electrode for welding were welded together, they were folded on the insulating material.

Next, after putting 45 mg of nonaqueous electrolyte (LiPF ₆ dissolved in a mixed solvent of ethylene carbonate and methyl ethyl carbonate in a volume ratio of 1: 2 at a concentration of 1.2 mol / l) in a sealing case. A flat non-aqueous secondary battery having the same structure as in FIGS. 1 and 2 except that the outer case is covered, the periphery is caulked, the diameter is 9.0 mm, the thickness is 5.4 mm, and the number of stacked positive and negative electrodes is different. Got. In the flat non-aqueous secondary battery, the difference between the inner diameter of the insulating gasket and the maximum diameter of the main body in the negative electrode is 0.1 mm.

Comparative Example 1
13 battery positive electrodes housed in the same bag-shaped separator as used in Example 1, and 12 battery negative electrodes having a negative electrode mixture layer formed on both sides of the same current collector as used in Example 1 And two negative electrodes for a battery having a negative electrode mixture layer formed on one side of the same current collector as used in Example 1, and a negative electrode for a battery having a negative electrode mixture layer formed on one side of the current collector. These positive electrodes for batteries and negative electrodes for batteries were alternately stacked so as to be the outermost electrode. However, for one of the negative electrodes for a battery in which a negative electrode mixture layer is formed on one surface of the current collector, an insulating material (PET film having a thickness of 0.1 mm) is attached to the exposed surface of the current collector. A punched one was used.

  Then, the main body part is bound with PP adhesive tape so that all the stacked electrodes are not displaced, and then the current collecting tabs of each battery negative electrode are welded together to form the outermost battery negative electrode. Of these, it was folded back on the side where the insulating material was not attached to the exposed surface of the current collector (on the exposed surface of the current collector). In addition, the current collector tabs of each battery positive electrode are welded together and folded back on the outermost battery negative electrode on which the insulating material is attached to the exposed surface of the current collector (on the insulating material) Thus, an electrode group was obtained.

  And the electrode group was inserted in the same exterior case as what was used in Example 1. FIG. In addition, the same sealing case and insulating gasket as those used in Example 1 were used, the insulating gasket was attached to the sealing case, and 45 mg of the same nonaqueous electrolytic solution as that used in Example 1 was added, and then the electrode group A flat non-aqueous secondary battery was produced by covering and caulking with an outer case into which was inserted.

Comparative Example 2
A positive electrode for a battery was produced in the same manner as in Example 1 except that the diameter (maximum diameter) of the arc portion was 5.5 mm. The battery positive electrode was accommodated. However, the diameter (maximum diameter) of the arc portion of the main portion of the bag-shaped separator containing the battery positive electrode was 6.5 mm. A negative electrode for a battery was produced in the same manner as in Example 1 except that the diameter (maximum diameter) of the arc portion was 6.5 mm.

  Then, a flat nonaqueous secondary battery was produced in the same manner as in Comparative Example 1 except that these battery positive electrode (battery positive electrode housed in a bag-shaped separator) and battery negative electrode were used. In the flat non-aqueous secondary battery, the difference between the inner diameter of the insulating gasket and the maximum diameter of the main body portion of the negative electrode is 0.8 mm.

  The flat non-aqueous secondary batteries of Examples and Comparative Examples were subjected to the following discharge capacity measurement and leakage resistance test. These results are shown in Table 1.

<Discharge capacity measurement>
About each battery of an Example and a comparative example, the constant current charge until a voltage will be 4.20V with a current value of 2 mA, and the constant voltage until a current value will be 0.6 mA with a voltage of 4.20V following that Then, the capacity was measured when the battery was discharged until the voltage reached 3 V at a current value of 2 mA. The discharge capacity was measured for 10 batteries, and the average value was taken as the discharge capacity of each battery.

<Leakage resistance test>
For each of the batteries of the example and comparative example (10 each), constant current charging until the voltage reached 4.20 V at a current value of 2 mA, followed by a current value of 0.6 mA at a voltage of 4.20 V Then, the battery was stored in an environment of 60 ° C. and a relative humidity of 90%, and the state of leakage during that time was observed.

  As shown in Table 1, the battery of Example 1 has a large capacity, and a defective product that causes leakage during storage has not been obtained, and the productivity is good.

  On the other hand, the battery of Comparative Example 1 uses the same size electrode as the Example and has a large capacity, but leaks during storage, resulting in poor productivity. When these batteries were disassembled, any of the binding tape, the negative current collecting tab portion, and the positive current collecting tab portion was caught between the outer case and the insulating packing. Further, the battery of Comparative Example 2 in which the difference between the inner diameter of the insulating gasket and the maximum diameter of the main body of the negative electrode is large, a defective product that causes leakage during storage has not been obtained, and the productivity is good. However, the capacity is small.

DESCRIPTION OF SYMBOLS 1 Flat type non-aqueous secondary battery 2 Exterior case 3 Sealing case 4 Insulating gasket 5 Positive electrode 5a Positive electrode main body 5b Positive electrode current collecting tab portion 6, 6A, 6B Negative electrode 6a Negative electrode main body portion 6b Negative electrode current collecting tab portion 7 Separator 7c Joint 8 Insulating material

Claims (7)

A plurality of positive electrodes and a plurality of negative electrodes are alternately arranged via separators in a space formed by caulking and sealing a circular outer case in plan view and a circular sealing case in plan view through an insulating gasket. And an electrode group laminated substantially parallel to the flat surface of the outer case and the sealing case, and a flat non-aqueous secondary battery having a non-aqueous electrolyte,
The positive electrode has a main body portion and a current collecting tab portion that protrudes from the main body portion in a plan view and is narrower than the main body portion. The main body portion of the positive electrode includes a current collector. A positive electrode mixture layer containing a positive electrode active material is formed on one side or both sides, and in the current collector tab portion of the positive electrode, a positive electrode mixture layer is not formed on the current collector,
The negative electrode has a main body portion and a current collecting tab portion that protrudes from the main body portion in a plan view and is narrower than the main body portion. The main body portion of the negative electrode includes a current collector. A negative electrode layer containing a negative electrode active material is formed on one side or both sides, and in the current collector tab portion of the negative electrode, the negative electrode layer is not formed on the current collector,
The electrode group does not have a binding tape that stops the whole,
A flat non-aqueous secondary battery, wherein a difference between an inner diameter of the insulating gasket and a maximum diameter of a main body of a negative electrode included in the electrode group is 0.01 to 0.2 mm. The outer case also serves as the positive terminal, and the sealing case also serves as the negative terminal.
The electrodes located on the outermost side of the electrode group are both negative electrodes, and the two negative electrodes located on the outermost side of the electrode group have a surface opposite to the outermost side of the electrode group in the main body. The negative electrode layer is formed only on the outermost surface of the electrode group in the main body and the current collecting tab portion, and the negative electrode layer is not formed on the current collector,
A negative electrode layer is formed on both surfaces of the main body of the negative electrode other than the negative electrode on the outermost side of the electrode group, and the negative electrode layer is not formed on the current collector tab portion. ,
In the electrode group, the current collecting tab portions of the negative electrode are gathered and folded on the negative electrode located on the outermost side on the outer case side in the electrode group, and the outer case of each current collecting tab portion of the folded negative electrode An insulating material is arranged on the side, and the exposed surface on the sealing case side of the current collector in the negative electrode located on the outermost side on the sealing case side in the electrode group is electrically connected to the inner surface of the sealing case. And
The flat non-aqueous water according to claim 1, wherein the current collecting tab portions of the positive electrode are gathered and folded on the insulating material disposed on the outer case side in the electrode group to be electrically connected to the outer case. Secondary battery. At least a separator made of a microporous film made of a thermoplastic resin is disposed on both sides of the positive electrode facing both sides of the negative electrode,
The two separators include a main body that covers the entire surface of the main body of the positive electrode, and an overhang that protrudes from the main body and covers at least a portion of the current collecting tab of the positive electrode that includes a boundary with the main body. 3. The flat non-aqueous secondary according to claim 1, wherein the two separators have a joined portion welded to each other at least at a part of a peripheral portion of a main portion thereof. 4. battery.   The flat non-aqueous secondary battery according to claim 3, wherein a joint portion between two separators disposed on both surfaces of the positive electrode is formed by directly welding the two separators.   The joining portion in the two separators arranged on both surfaces of the positive electrode is formed by welding through a layer made of the same type of resin as the thermoplastic resin constituting the two separators. The flat non-aqueous secondary battery described.   The flat nonaqueous secondary battery according to any one of claims 3 to 5, wherein the thermoplastic resin constituting the separator is polyolefin. A method for producing the flat non-aqueous secondary battery according to claim 1,
A flat structure comprising a step of forming a group of electrodes by sequentially inserting and laminating a negative electrode and a positive electrode in a sealing case fitted with an insulating gasket so that a separator is interposed between the negative electrode and the positive electrode. Of manufacturing a nonaqueous secondary battery.